The proposed research program focuses specifically on the role of cavitation in lithotripsy. Although purely mechanical processes may be primiarily responsible for the break-up kidney stones by intense shock waves, it is clear that the pressures involved greatly exceed the thresholds for transient cavitation. Cavitation is probably responsible for many of the reported side efforts of the treatment and even may play a role in reduction of the stones. As used here, the term lithotripsy includes all of the physical and biological phenomena associated with the intense shock waves of the modern clinical devices called lithotripters and hence the proposal is much broarder in its implications than the specific applications which these devices have found in clinical medicine up to the present time. To study cavitation in lithotropter fields, it will be necessary to consider all mechanisms by which shock waves interact with tissues. The specific aims in greater detail include (a) Development of relatively inexpensive, convenient and reliable, custom built, focused and spherically divergent, spark- generated and piezoelectric sources for use in the proposed experimental studies, (b) Development of acoustic and optical methods for measurement of the shock fields, (c) Develop and test theoretical models of shock wave propagation, (d) Develop and test models for the interaction of bubbles with shock waves, (e) Use lower organisms such as multicellular spheroids and insert for biological tests of theroetical predictions, (f) Study the effects of shok-induced cavitation in representative vertebrates, and (g) Investigate the mechanisms of fracture of kidney stones by shock fields and determine the causes of reported side efforts of these procedures.